A frontal depression is a large low-pressure weather system formed when warm air and cold air masses meet along a front, usually in middle and high latitudes. It is also called a mid-latitude cyclone or extratropical cyclone.
The system develops when warm, lighter air rises over colder, denser air, causing a drop in atmospheric pressure. As the pressure decreases, winds begin circulating around the low-pressure center counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

A frontal depression normally contains:
• Warm Front – Produces widespread clouds, fog, and steady rainfall.
• Cold Front – Causes heavy rain, thunderstorms, strong winds, and sudden temperature drops.
• Warm Sector – The warmer area located between the two fronts.
Frontal depressions are important weather systems because they bring changing weather conditions, rough seas, strong winds, and precipitation that can affect marine navigation and coastal operations.